The price jump from stage 2 to stage 3 is going to be substantial, not to mention to take advantage of the power these turbos support you need to upgrade a LOT of areas on your car, if that makes you feel any better about your choice...

Thank you for acknowledging that it's not sufficient to simply throw on bigger turbos (or turbo) then point and shoot.

Thought about making 5 bolt cast downpipes? Probably would help with tolerances a bit better..

Well, its not that close. If we are going 5 bolt, which we are we are just going to have SS downpipes made. The cost of having DP's cast will drive the price way up. Were trying to keep this kit affordable for you guys.

The turbo options I have announced for the kit have well established HP numbers they can support. This means SUPPORT, what each individual will actually see if a different story, based on upgrades, tune, etc, etc. But we will be doing our best to have a base tune ready for purchase right out of the gate so you can get up and running pretty easily. We will see what, if any tuning bugs we run into. But we plan on getting this prototype in the hands of a good tuner as soon as its ready to go.

The thing with these larger turbo upgrades is lag. Everyone including myself looks at Shiv's dyno and laughs because his peak HP lasts, what, 500 RPM? He's hitting redline at peak HP, not to mention he's not hitting full boost till like 5k RPMs. That's only 2500 RPMs at peak boost. The way to take advantage of this is more RPMs. This means springs and retainers and it means upgraded connecting rods. That ST would be a whole different animal revving out to at least 8500. That'd give you 3500 RPM at peak boost as opposed to 2500 RPMs. The point is, even with this TT upgrade, you're not taking advantage of the turbos efficiency range without some more serious upgrades to the N54. Driving my first big turbo car I have witnessed this first hand now. You can't have huge power and no lag. If you want to counter lag you move your RPM band right or you get more displacement to get the turbo to spool faster. Since i don't expect any stroker motors coming out any time soon, someone really needs to start thinking about putting some pistons, rods, springs and retainers in the car.

bigdnno,
I just saw this post. This is EXACTLY what i was getting at with the thread I just started and you already replied to. Big turbo cars are a drag on the street. Like most on this board, I like a quick car but I don't think that is typically the primary reason people buy BMWs.

The problem isn't the turbo size, it's the tuning. He was limiting boost in the midrange/mid high rev range to keep TQ down. And if @dzenno's car is any indicator, it seems to be able to take a pretty serious amount of tq in the midrange, which should allow one to run a much more normal boost curve. Now, I'm not saying that with a different approach that one will see a 62mm turbo full spooling at 2500 (that said, a video he posted seemed to make about 1 bar at 3100-3200). But when one isn't limiting throughout the rev range and runs a flatter boost curve, the power curve is going to look very different.

The problem isn't the turbo size, it's the tuning. He was limiting boost in the midrange/mid high rev range to keep TQ down. And if @dzen no's car is any indicator, it seems to be able to take a pretty serious amount of tq in the midrange, which should allow one to run a much more normal boost curve. Now, I'm not saying that with a different approach that one will see a 62mm turbo full spooling at 2500 (that said, a video he posted seemed to make about 1 bar at 3100-3200). But when one isn't limiting throughout the rev range and runs a flatter boost curve, the power curve is going to look very different.

For people that do not know or feel like looking it up. 1 bar is 14.5 PSI. The fight with turbo lag is one that is nothing new. In theory these highly efficient GTX twins should offer quicker spool over a big single. In practice we really wont know til we have it running on a N54 because its never been done.